feat(adapters): external adapter plugin system with dynamic UI parser

- Plugin loader: install/reload/remove/reinstall external adapters
  from npm packages or local directories
- Plugin store persisted at ~/.paperclip/adapter-plugins.json
- Self-healing UI parser resolution with version caching
- UI: Adapter Manager page, dynamic loader, display registry
  with humanized names for unknown adapter types
- Dev watch: exclude adapter-plugins dir from tsx watcher
  to prevent mid-request server restarts during reinstall
- All consumer fallbacks use getAdapterLabel() for consistent display
- AdapterTypeDropdown uses controlled open state for proper close behavior
- Remove hermes-local from built-in UI (externalized to plugin)
- Add docs for external adapters and UI parser contract

ui/src/components/InstanceSidebar.tsx

@@ -1,5 +1,5 @@
 import { useQuery } from "@tanstack/react-query";
-import { Clock3, FlaskConical, Puzzle, Settings, SlidersHorizontal } from "lucide-react";
+import { Clock3, Cpu, FlaskConical, Puzzle, Settings, SlidersHorizontal } from "lucide-react";
 import { NavLink } from "@/lib/router";
 import { pluginsApi } from "@/api/plugins";
 import { queryKeys } from "@/lib/queryKeys";
@@ -26,6 +26,7 @@ export function InstanceSidebar() {
           <SidebarNavItem to="/instance/settings/heartbeats" label="Heartbeats" icon={Clock3} end />
           <SidebarNavItem to="/instance/settings/experimental" label="Experimental" icon={FlaskConical} />
           <SidebarNavItem to="/instance/settings/plugins" label="Plugins" icon={Puzzle} />
+          <SidebarNavItem to="/instance/settings/adapters" label="Adapters" icon={Cpu} />
           {(plugins ?? []).length > 0 ? (
             <div className="ml-4 mt-1 flex flex-col gap-0.5 border-l border-border/70 pl-3">
               {(plugins ?? []).map((plugin) => (